Choosing heat-rejection film for your home

What you'll learn

• What TSER and VLT ratings actually mean and which one predicts cooling performance
• How window orientation changes which film spec matters most
• Why clear UV film differs from heat-rejection film and which one you actually need
• How to get accurate quotes by measuring your windows before calling an installer

Step by step

1. Identify your problem windows by orientation West-facing windows get the most intense afternoon heat in San Diego because the sun is low in the sky and shining directly into the glass from roughly 2 PM to sunset. South-facing windows get more consistent full-day exposure. East-facing windows are primarily a morning problem. Map your windows before calling an installer so you can describe exactly where the heat and glare are worst.
2. Read the TSER rating, not just the VLT TSER stands for Total Solar Energy Rejected and measures what percentage of total solar energy the film keeps out. A film with 60% TSER blocks 60% of the solar energy hitting the glass. VLT tells you how dark the film looks, not how much heat it rejects. Two films with identical VLT can have very different TSER ratings depending on film technology. Request TSER numbers when comparing film options.
3. Match the film darkness to your daylight needs A 15% VLT film blocks more light than a 50% VLT film and looks noticeably darker from the street. On a bedroom or bathroom window facing west, a darker film may be ideal. On a living room picture window facing south where natural light is part of what you like about the room, a lighter film (35-50% VLT) with a high TSER ceramic construction may give you most of the heat reduction without making the room dim.
4. Check your windows for low-e glass before ordering Many homes built after 2000 have dual-pane low-e glass, which already rejects some solar heat. Adding certain solar control films to low-e glass can cause heat to build up between the panes and break the seal over time. Ask your installer to verify whether your windows are low-e before selecting a film. Most manufacturers have approved film lists for low-e applications.
5. Get square footage measurements before calling for quotes Installers quote by the square foot. Measure each window's width and height in inches, multiply to get square inches, then divide by 144 to convert to square feet. Add 10% for cuts and waste. Having accurate measurements speeds up the quote process and lets you compare bids fairly, since installers quoting the same square footage will be pricing the same job.